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Date: Tue, 12 Nov 2013 08:25:02 -0700 From: David Ahern <dsahern@...il.com> To: Peter Zijlstra <peterz@...radead.org> CC: Ingo Molnar <mingo@...nel.org>, acme@...stprotocols.net, linux-kernel@...r.kernel.org, Frederic Weisbecker <fweisbec@...il.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Mike Galbraith <efault@....de>, Stephane Eranian <eranian@...gle.com> Subject: Re: [PATCH] perf record: Delete file if a failure occurs writing the perf data file On 11/12/13, 8:04 AM, Peter Zijlstra wrote: > On Tue, Nov 12, 2013 at 07:51:16AM -0700, David Ahern wrote: >>> From man mmap: >>> SIGBUS Attempted access to a portion of the buffer that >>> does not correspond to the file (for example, beyond >>> the end of the file, ... > > SIGBUS is basically the std fail for any fault; there's a ton more > reasons than listed in that manpage. > > Failing to dirty a page due to -ENOSPACE is one reason we'll > trigger SIGBUS -- as you already found in that memcpy to mmap() instead > of write() patch. Sure. Lots of mmaps flying around, so to make sure we are on the same page in this case we are talking about perf-report reading a file via mmap. If the file creation (be it memcpy to mmap() or write()) has a failure due to lack of space, then only a partial event is in the file -- e.g., perf-header only. Trying to read the rest of the event leads to perf-report terminating due to SIGBUS. How should that condition be handled? The patch in this thread deletes the file. Another option is to rewind the file to the last known good write (ie., length after last successful call to write_output). David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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